• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.1
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• pp.1-10
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• 1983

The photoelastic determination of S.I.F. in Fracture mechanics has been regarded as one of the most effective and practical experimental methods in which stresses are read directly, except a few shortcomings involved in the process of experiment; the difficulties of making a sharp crack tip similar to the practical one and nearly impossibilities of carving an arbitrarily shaped crack on the test plate, etc. To eliminate flaws mentioned above, recently, Kitagawa and Watanabe of Tokyo Univ.developed a new method named"Teflon Insert Method". which has improved experimental accuracy to a considerable extent byt remaining still room for further improvement, that is, the elimination of bonding boundary scars which render photoelastic fringes obscure. In this paper, a newly exploited"Teflon Molding Method" was attempted for the completion of teflon-epoxy experimental method. The experimental results obtained by this method are compared with existent theoretical and experimental values to evaluate its accuracy. As result, 1-6% of margin of errors were appeared in a series of photoelastic experiments which defied any other conventional method in terms of experimental accuracy.perimental accuracy.

• Smart Structures and Systems
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• v.4 no.5
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• pp.629-640
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• 2008

A new algorithm is proposed to determine optimal accelerometer locations (OAL) when a structure is identified by frequency domain system identification (SI) method. As a result, a guideline is presented for selecting OAL which can reflect modal response of a structure properly. The guideline is to provide a minimum number of necessary accelerometers with the variation in the number of measurable target modes. To determine OAL for SI applications effectively, the modal sensitivity effective independence distribution vector (MS-EIDV) is developed with the likelihood function of measurements. By maximizing the likelihood of the occurrence of the measurements relative to the predictions, Fisher Information Matrix (FIM) is derived as a function of mode shape sensitivity. This paper also proposes a statistical approach in determining the structural parameters with a presumed parameter error which reflects the epistemic paradox between the determination of OAL and the application of a SI scheme. Numerical simulations have been carried out to examine the proposed OAL algorithm. A two-span multi-girder bridge and a two-span truss bridge were used for the simulation studies. To overcome a rank deficiency frequently occurred in inverting a FIM, the singular value decomposition scheme has been applied.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.363-367
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• 2009

An isotope-dilution flow-injection electrospray/mass spectrometric method was developed for the accurate determination of glucosamine contents in pharmaceutical formulations. Samples were extracted by methanol. After spiking glucosamine-1-$^{13}C_1$ as an internal standard, the extracts were then analyzed by flow-injection ESI/MS in a selected ion monitoring (SIM) mode to detect [M+H]$^+$ ions of the analyte and its isotope analogue at m/z 180 and m/z 181, respectively. Confirmatory measurements were made by selectively monitoring the collisionally induced dissociation channels of m/z 180 $\rightarrow$ m/z 72 and m/z 181 $\rightarrow$73, respectively, to test the possibility of bias in the SIM method due to matrix interferences, but any significant bias in the SIM mode was not observed. Repeatability and reproducibility studies showed that the flow-injection ESI/MS method is a reliable and reproducible method which can provide a typical method precision of 1.0 %. Other results for the method validation are reported.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.315-320
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• 2012

In H.264/AVC, the first frame of a group of pictures (GOP) is encoded in intra mode which generates a large number of bits. The number of bits for the I-frame affects the qualities of the following frames of a GOP since they are encoded using the bits remaining among the bits allocated to the GOP. In addition, the first frame is used for the inter mode encoding of the following frames. Thus, the initial quantization parameter (QP) affects the following frames as well as the first frame. In this paper, an adaptive peak signal to noise ratio (PSNR)-based initial QP determination algorithm is presented. In the proposed algorithm, a novel linear model is established based on the observation of the relation between the initial QPs and PSNRs of frames. Using the linear model and PSNR results of the encoded GOPs, the proposed algorithm accurately estimates the optimal initial QP which maximizes the PSNR of the current GOP. It is shown by experimental results that the proposed algorithm predicts the optimal initial QP accurately and thus achieves better PSNR performance than that of the existing algorithm.

• Mass Spectrometry Letters
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• v.9 no.4
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• pp.95-99
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• 2018

An innovative, simple, and rapid assay method based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was developed and validated for the simultaneous determination of eight statin drugs in human urine. A simple sample clean-up procedure using the "dilute and shoot" (DAS) approach enabled a fast and reliable analysis. The influence of the dilution factor was investigated to ensure detectability and reduce the matrix effect. Chromatographic separation was performed on a Phenomenex Kinetex C18 column ($50{\times}3.0mm$ i.d., $2.6{\mu}m$) using an elution gradient of mobile phase A composed of 0.1% acetic acid, and mobile phase B composed of acetonitrile, at a flow rate of 0.35 mL/min. Quantitation was performed on a triple quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode using electrospray ionization in positive ion mode. The total chromatographic run time was 15 min. The method was validated for selectivity, sensitivity, recovery, linearity, accuracy, precision, and stability. The present method was successfully applied to the analysis of Rosuvastatin in urine samples after oral administration to healthy human subjects.

• Journal of Preventive Medicine and Public Health
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• v.17 no.1
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• pp.269-279
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• 1984

The optimum conditions for measuring cadmium content of less than 0.2ppm by flame atomic absorption spectrophotometry were investigated. The cadmium in urine was extracted by APDC-MIBK for the analysis by atomic absorption spectrophotometry after ashing them by a wet method. 1. Optimum conditions by APDC-MIBK and DDTC-MIBK extractions. The acidic aqueous solution was prepared with appropriate amount of 0.IN nitric acid, 5ml of 25% (W/V) sodium potasstum tartarate, 10ml of saturated ammonium sulfate, and 2ml of 2% APDC(or 1 ml of 5% DDTC) chelating agent. The total volume of solution was adjusted to 55 ml and pH to $2{\sim}10$ (or$7{\sim}10$). The aqueous solution was extracted with 10ml MIBK. Concentration of Triton X-100 did not effect the absorbance for APDC-MIBK extraction of cadmium, but absorbance decreased as the concentration increased for DDTC-MIBK extraction. The sensitivity and detection limits for the cadmium determination from APDC-MIBK extraction were 0.0038ppm and 0.0102, 0.0022ppm and 0.0116 for DDTC-MIBK, and 0.0132ppm and 0.0034 for 0.1N nitric acid. APDC-MIBK and DDTC-MIBK extractions were 3 times higher than 0.1N nitric acid for the sensitivity. 2. Excretion of cadmium in 24-hour urine by APDC-MIBK extraction. Determination of cadmium in urine by atomic absorption spectrophotometry of A.A. (Cd=2 mA) mode and B.C. (Cd=4 mA) mode and B.C. (Cd=4mA, $D_2=20mA$) mode showed some difference (p<0.05). The difference of cadmium determination and recovery according to method of standard additions and standard calibration curve method in urine was not significant (p>0.05, $93.48{\pm}11.78%,\;94.83{\pm}22.00%$). Excretion of cadmium in 24-hour urine collection from normal person and variance analysis within measurement variation was not significant (p>0.05), but between interindividual was significant (0.05). Determination of cadmium content by two different methods of flame atomic absorption spectrophotometry and dithizone colorimetry showed that the results from the two methods can be described by a regression line with a good correlation (y=1.0153x-0.2927, x=Cd by D.C., y=Cd by A.A.S., $r=0.8651^*$, p<0.01).

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.178-185
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• 2005

Crack tip displacement is originated by tensile stress component, s and shear stress component, t on pure Mode I and pure Mode II. The crack tip displacement(CTD) depends on combined types of different two stress components under mixed-mode loading conditions (MMLC). Thus, the analysis of crack tip displacement must be CTD vector, dv which is composition of ds and dt under MMLC. In this paper, various effects of MMLC on the crack closure are studied experimentally. The crack closure magnitude is calculated from the information of crack tip displacement under MMLC. This information has been obtained from the high resolution optical microscope in direct observations of crack displacement behavior at the crack tip. Observed crack tip displacement is analyzed by using CTD vector to determine crack opening load. The various effects of MMLC on the crack closure are explained using crack opening ratio with crack length and mode mixture. The effective stress intensity factor considering crack closure is also discussed.

• Journal of Power Electronics
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• v.17 no.4
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• pp.991-1003
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• 2017

The conventional sliding mode control (CSMC) has a number of problems. It may cause dc output voltage ripple and it cannot guarantee the robustness of the whole system for a matrix rectifier (MR). Furthermore, the existence of a filter can decrease the input power factor (IPF). Therefore, a novel global sliding mode control (GSMC) based on a hyperbolic tangent function with IPF compensation for MRs is proposed in this paper. Firstly, due to the reachability and existence of the sliding mode, the condition of the matrix rectifier's robustness and chattering elimination is derived. Secondly, a global switching function is designed and the determination of the transient operation status is given. Then a SMC compensation strategy based on a DQ transformation model is applied to compensate the decreasing IPF. Finally, simulations and experiments are carried out to verify the correctness and effectiveness of the control algorithm. The obtained results show that compared with CSMC, applying the proposed GSMC based on a hyperbolic tangent function for matrix rectifiers can achieve a ripple-free output voltage with a unity IPF. In addition, the rectifier has an excellent robust performance at all times.

• Journal of Power Electronics
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• v.15 no.3
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• pp.634-643
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• 2015

This paper presents a high frequency design approach for improving efficiency over a wide load range in the self-driven phase-shifted full-bridge converters for server power systems. In the proposed approach, a detailed ZVS analysis of the lagging leg switches in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM) is presented. The optimum dead time and the determination of the appropriate operation mode are given for high efficiency according to the load conditions. Finally, the optimum operation conditions are defined to achieve a high-efficiency. A laboratory prototype operating at 80 kHz, rated 1 kW (12 V-83.3 A), is built to verify proposed theoretical analysis and evaluations. The experimental results show that the maximum efficiency is achieved as 95% and 83.5% at full load and 5% load conditions, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.199-203
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• 2012

This paper introduces a simple new procedure approach to determine the permittivity of dielectric slabs. The method uses a parallel plate waveguide which supports a TEM mode. The presence of the dielectric slab placed at the bottom of the waveguide makes the speed of the TEM wave slower. The relationship between the change of the speed and the permittivity of the dielectric slab allows the determination of the permittivity. The relationship is analyzed electromagnetically, and the results of measurements are in good agreement with the analysis.